datacursor.java

嵌入式数据库Berkeley DB-4.5.20源代码

/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 2000-2006
 *      Oracle Corporation.  All rights reserved.
 *
 * $Id: DataCursor.java,v 12.7 2006/09/08 20:32:13 bostic Exp $
 */

package com.sleepycat.collections;

import com.sleepycat.compat.DbCompat;
import com.sleepycat.db.Cursor;
import com.sleepycat.db.CursorConfig;
import com.sleepycat.db.DatabaseEntry;
import com.sleepycat.db.DatabaseException;
import com.sleepycat.db.JoinConfig;
import com.sleepycat.db.JoinCursor;
import com.sleepycat.db.LockMode;
import com.sleepycat.db.OperationStatus;
import com.sleepycat.util.keyrange.KeyRange;
import com.sleepycat.util.keyrange.RangeCursor;

/**
 * Represents a Berkeley DB cursor and adds support for indices, bindings and
 * key ranges.
 *
 * <p>This class operates on a view and takes care of reading and updating
 * indices, calling bindings, constraining access to a key range, etc.</p>
 *
 * @author Mark Hayes
 */
final class DataCursor implements Cloneable {

    /** Repositioned exactly to the key/data pair given. */
    static final int REPOS_EXACT = 0;
    /** Repositioned on a record following the key/data pair given. */
    static final int REPOS_NEXT = 1;
    /** Repositioned failed, no records on or after the key/data pair given. */
    static final int REPOS_EOF = 2;

    private RangeCursor cursor;
    private JoinCursor joinCursor;
    private DataView view;
    private KeyRange range;
    private boolean writeAllowed;
    private boolean readUncommitted;
    private DatabaseEntry keyThang;
    private DatabaseEntry valueThang;
    private DatabaseEntry primaryKeyThang;
    private DatabaseEntry otherThang;
    private DataCursor[] indexCursorsToClose;

    /**
     * Creates a cursor for a given view.
     */
    DataCursor(DataView view, boolean writeAllowed)
        throws DatabaseException {

        init(view, writeAllowed, null, null);
    }

    /**
     * Creates a cursor for a given view.
     */
    DataCursor(DataView view, boolean writeAllowed, CursorConfig config)
        throws DatabaseException {

        init(view, writeAllowed, config, null);
    }

    /**
     * Creates a cursor for a given view and single key range.
     * Used by unit tests.
     */
    DataCursor(DataView view, boolean writeAllowed, Object singleKey)
        throws DatabaseException {

        init(view, writeAllowed, null, view.subRange(view.range, singleKey));
    }

    /**
     * Creates a cursor for a given view and key range.
     * Used by unit tests.
     */
    DataCursor(DataView view, boolean writeAllowed,
               Object beginKey, boolean beginInclusive,
               Object endKey, boolean endInclusive)
        throws DatabaseException {

        init(view, writeAllowed, null,
             view.subRange
                (view.range, beginKey, beginInclusive, endKey, endInclusive));
    }

    /**
     * Creates a join cursor.
     */
    DataCursor(DataView view, DataCursor[] indexCursors,
               JoinConfig joinConfig, boolean closeIndexCursors)
        throws DatabaseException {

        if (view.isSecondary()) {
            throw new IllegalArgumentException(
                "The primary collection in a join must not be a secondary " +
                "database");
        }
        Cursor[] cursors = new Cursor[indexCursors.length];
        for (int i = 0; i < cursors.length; i += 1) {
            cursors[i] = indexCursors[i].cursor.getCursor();
        }
        joinCursor = view.db.join(cursors, joinConfig);
        init(view, false, null, null);
        if (closeIndexCursors) {
            indexCursorsToClose = indexCursors;
        }
    }

    /**
     * Clones a cursor preserving the current position.
     */
    DataCursor cloneCursor()
        throws DatabaseException {

        checkNoJoinCursor();

        DataCursor o;
        try {
            o = (DataCursor) super.clone();
        } catch (CloneNotSupportedException neverHappens) {
            return null;
        }

        o.initThangs();
        KeyRange.copy(keyThang, o.keyThang);
        KeyRange.copy(valueThang, o.valueThang);
        if (primaryKeyThang != keyThang) {
            KeyRange.copy(primaryKeyThang, o.primaryKeyThang);
        }

        o.cursor = cursor.dup(true);
        return o;
    }

    /**
     * Returns the internal range cursor.
     */
    RangeCursor getCursor() {
        return cursor;
    }

    /**
     * Constructor helper.
     */
    private void init(DataView view,
                      boolean writeAllowed,
                      CursorConfig config,
                      KeyRange range)
        throws DatabaseException {

        if (config == null) {
            config = view.cursorConfig;
        }
        this.view = view;
        this.writeAllowed = writeAllowed && view.writeAllowed;
        this.range = (range != null) ? range : view.range;
        readUncommitted = config.getReadUncommitted() ||
                          view.currentTxn.isReadUncommitted();
        initThangs();

        if (joinCursor == null) {
            cursor = new MyRangeCursor
                (this.range, config, view, this.writeAllowed);
        }
    }

    /**
     * Constructor helper.
     */
    private void initThangs()
        throws DatabaseException {

        keyThang = new DatabaseEntry();
        primaryKeyThang = view.isSecondary() ? (new DatabaseEntry())
                                             : keyThang;
        valueThang = new DatabaseEntry();
    }

    /**
     * Set entries from given byte arrays.
     */
    private void setThangs(byte[] keyBytes,
                           byte[] priKeyBytes,
                           byte[] valueBytes) {

        keyThang.setData(KeyRange.copyBytes(keyBytes));

        if (keyThang != primaryKeyThang) {
            primaryKeyThang.setData(KeyRange.copyBytes(priKeyBytes));
        }

        valueThang.setData(KeyRange.copyBytes(valueBytes));
    }

    /**
     * Closes the associated cursor.
     */
    void close()
        throws DatabaseException {

        if (joinCursor != null) {
            JoinCursor toClose = joinCursor;
            joinCursor = null;
            toClose.close();
        }
        if (cursor != null) {
            Cursor toClose = cursor.getCursor();
            cursor = null;
            view.currentTxn.closeCursor(toClose );
        }
        if (indexCursorsToClose != null) {
            DataCursor[] toClose = indexCursorsToClose;
            indexCursorsToClose = null;
            for (int i = 0; i < toClose.length; i += 1) {
                toClose[i].close();
            }
        }
    }

    /**
     * Repositions to a given raw key/data pair, or just past it if that record
     * has been deleted.
     *
     * @return REPOS_EXACT, REPOS_NEXT or REPOS_EOF.
     */
    int repositionRange(byte[] keyBytes,
                        byte[] priKeyBytes,
                        byte[] valueBytes,
                        boolean lockForWrite)
        throws DatabaseException {

        LockMode lockMode = getLockMode(lockForWrite);
        OperationStatus status = null;

        /* Use the given key/data byte arrays. */
        setThangs(keyBytes, priKeyBytes, valueBytes);

        /* Position on or after the given key/data pair. */
        if (view.dupsAllowed) {
            status = cursor.getSearchBothRange(keyThang, primaryKeyThang,
                                               valueThang, lockMode);
        }
        if (status != OperationStatus.SUCCESS) {
            status = cursor.getSearchKeyRange(keyThang, primaryKeyThang,
                                              valueThang, lockMode);
        }

        /* Return the result of the operation. */
        if (status == OperationStatus.SUCCESS) {
            if (!KeyRange.equalBytes(keyBytes, 0, keyBytes.length,
                                     keyThang.getData(),
                                     keyThang.getOffset(),
                                     keyThang.getSize())) {
                return REPOS_NEXT;
            }
            if (view.dupsAllowed) {
                DatabaseEntry thang = view.isSecondary() ? primaryKeyThang
                                                         : valueThang;
                byte[] bytes = view.isSecondary() ? priKeyBytes
                                                  : valueBytes;
                if (!KeyRange.equalBytes(bytes, 0, bytes.length,
                                         thang.getData(),
                                         thang.getOffset(),
                                         thang.getSize())) {
                    return REPOS_NEXT;
                }
            }
            return REPOS_EXACT;
        } else {
            return REPOS_EOF;
        }
    }

    /**
     * Repositions to a given raw key/data pair.
     *
     * @throws IllegalStateException when the database has unordered keys or
     * unordered duplicates.
     *
     * @return whether the search succeeded.
     */
    boolean repositionExact(byte[] keyBytes,
                            byte[] priKeyBytes,
                            byte[] valueBytes,
                            boolean lockForWrite)
        throws DatabaseException {

        LockMode lockMode = getLockMode(lockForWrite);
        OperationStatus status = null;

        /* Use the given key/data byte arrays. */
        setThangs(keyBytes, priKeyBytes, valueBytes);

        /* Position on the given key/data pair. */
        if (view.recNumRenumber) {
            /* getSearchBoth doesn't work with recno-renumber databases. */
            status = cursor.getSearchKey(keyThang, primaryKeyThang,
                                         valueThang, lockMode);
        } else {
            status = cursor.getSearchBoth(keyThang, primaryKeyThang,
                                          valueThang, lockMode);
        }

        return (status == OperationStatus.SUCCESS);
    }

    /**
     * Returns the view for this cursor.
     */
    DataView getView() {

        return view;
    }

    /**
     * Returns the range for this cursor.
     */
    KeyRange getRange() {

        return range;
    }

    /**
     * Returns whether write is allowed for this cursor, as specified to the
     * constructor.
     */
    boolean isWriteAllowed() {

        return writeAllowed;
    }

    /**
     * Returns the key object for the last record read.
     */
    Object getCurrentKey()
        throws DatabaseException {

        return view.makeKey(keyThang, primaryKeyThang);
    }

    /**
     * Returns the value object for the last record read.
     */
    Object getCurrentValue()
        throws DatabaseException {

        return view.makeValue(primaryKeyThang, valueThang);
    }

    /**
     * Returns the internal key entry.
     */
    DatabaseEntry getKeyThang() {
        return keyThang;
    }

    /**
     * Returns the internal primary key entry, which is the same object as the
     * key entry if the cursor is not for a secondary database.
     */
    DatabaseEntry getPrimaryKeyThang() {
        return primaryKeyThang;
    }

    /**
     * Returns the internal value entry.
     */
    DatabaseEntry getValueThang() {
        return valueThang;
    }

    /**
     * Returns whether record number access is allowed.
     */
    boolean hasRecNumAccess() {

        return view.recNumAccess;
    }

    /**
     * Returns the record number for the last record read.
     */
    int getCurrentRecordNumber()
        throws DatabaseException {

        if (view.btreeRecNumDb) {
            /* BTREE-RECNO access. */
            if (otherThang == null) {
                otherThang = new DatabaseEntry();
            }
            DbCompat.getCurrentRecordNumber(cursor.getCursor(), otherThang,
                                            getLockMode(false));
            return DbCompat.getRecordNumber(otherThang);
        } else {
            /* QUEUE or RECNO database. */
            return DbCompat.getRecordNumber(keyThang);
        }
    }

    /**
     * Binding version of Cursor.getCurrent(), no join cursor allowed.
     */
    OperationStatus getCurrent(boolean lockForWrite)
        throws DatabaseException {

        checkNoJoinCursor();
        return cursor.getCurrent(keyThang, primaryKeyThang, valueThang,
                                 getLockMode(lockForWrite));
    }

    /**
     * Binding version of Cursor.getFirst(), join cursor is allowed.
     */
    OperationStatus getFirst(boolean lockForWrite)
        throws DatabaseException {

        LockMode lockMode = getLockMode(lockForWrite);
        if (joinCursor != null) {
            return joinCursor.getNext(keyThang, valueThang, lockMode);
        } else {
            return cursor.getFirst(keyThang, primaryKeyThang, valueThang,
                                   lockMode);
        }
    }

    /**
     * Binding version of Cursor.getNext(), join cursor is allowed.
     */
    OperationStatus getNext(boolean lockForWrite)
        throws DatabaseException {

        LockMode lockMode = getLockMode(lockForWrite);
        if (joinCursor != null) {
            return joinCursor.getNext(keyThang, valueThang, lockMode);
        } else {